Mobile irrigation machines having elevated boom or truss assemblies carrying multiple sprinklers are typically of the center-pivot type or the linear-move type. In a center-pivot machine, the elevated truss assembly pivots about an upright standpipe that supplies water to the sprinklers supported from the truss assembly. In a linear-move machine (referred to herein as a “linear irrigator”), the elevated truss assembly is carried on mobile, wheeled towers that move the machine along a substantially straight path that is generally perpendicular to the elevated boom or truss. Typically, a linear irrigator moves from one end of a field to the other and back again, sprinkling in one or both directions.
While linear irrigators can irrigate more area than center-pivot machines by reason of the resulting rectangularly-shaped irrigation pattern, linear irrigators have proven to be problematic in several respects. The most significant problem relates to the manner in which water is supplied to the machine. In some cases where the field is flat, the machine travels alongside an open ditch or canal from which water is continuously removed. Ditch water, however, typically contains significant amounts of dirt and/or debris that can clog the sprinkler nozzles. In other cases, one or more hoses are dragged by the machine the length of the field, requiring one or more manual attachment/detachment procedures and attendant issues of hose management. High pressure drops associated with such systems also lead to high energy costs. In still other cases, complex mechanisms have been proposed for automatic docking with hydrants spaced along the length of a water supply pipe. One of the problems with these latter arrangements is that the hydrant risers are held firmly in concrete or welded onto steel pipe, and misalignment with the docking mechanism can cause serious damage to the hydrant as well as to the docking mechanism. In some instances, the linear irrigator must be halted during an entire watering cycle at each successive hydrant. In others, continuous operation of the linear irrigator is said to be achieved, but the mechanisms employed to obtain continuity have been complex, costly and generally not commercially successful.
In commonly owned U.S. Pat. No. 7,300,004 a traveling sprinkler is disclosed that incorporates a “floating” docking station for automatically engaging and disengaging hydrant valves on a supply pipe. In commonly owned U.S. Pat. No. 7,140,563, a linear irrigator is disclosed that incorporates a similar docking station. A variation of that docking station that adds power actuators to assist in required lateral and vertical adjustments is disclosed in commonly-owned pending U.S Published Application No. 2006/0192037. These docking stations can be utilized with minor adaptations in the present invention. For the most part, in the patents and application identified above, only one docking station is utilized, so that the supply of water to the sprinklers is interrupted when the traveling sprinkler or linear irrigator moves from one hydrant to the next. In one instance, a pair of docking stations is used in a continuous water supply arrangement, but separate, parallel supply pipes are required.
Accordingly, there remains a need for a relatively simple and reliable hydrant docking arrangement for a linear irrigator that can engage and disengage successive hydrants in a continuous manner as the linear machine moves along its path of travel.